"

 COPYRIGHT (c) 1993 by Claus Gittinger

	      All Rights Reserved

 This software is furnished under a license and may be used

 only in accordance with the terms of that license and with the

 inclusion of the above copyright notice.   This software may not

 be provided or otherwise made available to, or used by, any

 other person.  No title to or ownership of the software is

 hereby transferred.

"

Parser subclass:#Explainer

	instanceVariableNames:''

	classVariableNames:''

	poolDictionaries:''

	category:'System-Compiler'

!

!Explainer class methodsFor:'documentation'!

copyright

"

 COPYRIGHT (c) 1993 by Claus Gittinger

	      All Rights Reserved

 This software is furnished under a license and may be used

 only in accordance with the terms of that license and with the

 inclusion of the above copyright notice.   This software may not

 be provided or otherwise made available to, or used by, any

 other person.  No title to or ownership of the software is

 hereby transferred.

"

!

documentation

"

    a very simple explainer - much more should be added ...

    This one is involved, when the 'explain' function is used in a 

    codeView (popup or via CMD-E).

    [author:]

        Claus Gittinger

"

! !

!Explainer class methodsFor:'explaining'!

commonSuperClassOf:listOfClassNames

    |common found|

    listOfClassNames do:[:className |

        |class|

        class := Smalltalk classNamed:className.

        common isNil ifTrue:[

            common := class

        ] ifFalse:[

            (class isSubclassOf:common) ifTrue:[

                "keep common"

            ] ifFalse:[

                (common isSubclassOf:class) ifTrue:[

                    common := class

                ] ifFalse:[

                    "walk up, checking"

                    found := false.

                    common allSuperclassesDo:[:sup |

                        (class isSubclassOf:sup) ifTrue:[

                            common := sup

                        ]

                    ].

                    found ifFalse:[

                        class allSuperclassesDo:[:sup |

                            (common isSubclassOf:sup) ifTrue:[

                                common := sup

                            ]

                        ].

                    ].

                ]

            ].

        ].

        common == Object ifTrue:[^ common]

    ].

    ^ common

    "Modified: 17.6.1996 / 17:09:21 / stefan"

    "Modified: 5.9.1996 / 19:34:41 / cg"

!

explain:someText in:source forClass:aClass

    "Given a source and a substring of it, return a string containing

     an explanation.

     This is just a q&d implementation - to be correct, it should use the parser,

     and explain from the parsetree (instead of doing string matches).

     This leads to some wrong explanations, for example if some string is

     used as selector within a string, or if a variable is named like a

     message selector. I.e. the explanation should be context sensitive.

     Also, there could be much more detailed explanations."

    |parser variables v c string tmp

     spc sym sel stringText|

    string := someText string withoutSeparators.

    stringText := string asText allBold.

    "

     ask parser for variable names

    "

    parser := self parseMethod:source in:aClass ignoreErrors:true ignoreWarnings:true.

    parser notNil ifTrue:[

        "look for variables"

        variables := parser methodVars.

        (variables notNil and:[variables includes:string]) ifTrue:[

            ^ '''' , stringText , ''' is a method variable'

        ].

        variables := parser methodArgs.

        (variables notNil and:[variables includes:string]) ifTrue:[

            ^ '''' , stringText , ''' is a method argument'

        ]

    ].

    parser isNil ifTrue:[

        parser := self for:(ReadStream on:source) in:aClass

    ].

    "instvars"

    c := aClass whichClassDefinesInstVar:string.

    c notNil ifTrue:[

        c isMeta ifTrue:[

            ^ '''' , stringText , ''' is a class instance variable in ' , c soleInstance name

        ].

        ^ '''' , stringText , ''' is an instance variable in ' , c name

    ].

"/    variables := aClass allInstVarNames.

"/    (variables notNil and:[variables includes:string]) ifTrue:[

"/        "where is it"

"/        c := aClass.

"/        [c notNil] whileTrue:[

"/            v := c instVarNames.

"/            (v notNil and:[v includes:string]) ifTrue:[

"/                ^ string , ' is an instance variable in ' , c name

"/            ].

"/            c := c superclass

"/        ].

"/        self error:'oops'

"/    ].

"/    "class instvars"

"/    variables := aClass class allInstVarNames.

"/    (variables notNil and:[variables includes:string]) ifTrue:[

"/        "where is it"

"/        c := aClass.

"/        [c notNil] whileTrue:[

"/            v := c class instVarNames.

"/            (v notNil and:[v includes:string]) ifTrue:[

"/                ^ string , ' is a class instance variable in ' , c name

"/            ].

"/            c := c superclass

"/        ].

"/        self error:'oops'

"/    ].

    "classvars"

    c := parser inWhichClassIsClassVar:string.

    c notNil ifTrue:[

        ^ '''' , stringText , ''' is a class variable in ' , c name

    ].

    aClass isMeta ifTrue:[

        c := aClass soleInstance.

    ] ifFalse:[

        c := aClass.

    ].

    c privateClasses do:[:pClass |

        (pClass name = string 

         or:[pClass nameWithoutPrefix = string]) ifTrue:[

            ^ ('''' , stringText , ''' is a private class in ''' , c name , '''.'

                     , '\\It is only visible locally.') withCRs

        ].

    ].

    (spc := aClass nameSpace) notNil ifTrue:[

        sym := (spc name , '::' , string) asSymbolIfInterned.

        sym notNil ifTrue:[

            (Smalltalk at:sym) isBehavior ifTrue:[

                ^ ('''' , stringText , ''' is a class in the ''' , spc name , ''' nameSpace.'

                         , '\\It is only visible within this nameSpace.'

                         , '\Access from the outside is possible'

                         , '\by the special name ''' , spc name , '::' , string , '''.') withCRs

            ].

        ].

    ].

"/    string knownAsSymbol ifTrue:[

        "globals & symbols"

        tmp := self explainKnownSymbol:string inClass:aClass.

        tmp notNil ifTrue:[ ^ tmp].

        "/ try with added colon ...

        sel := string , ':'.

        Symbol allInstancesDo:[:sym |

            (sym startsWith:sel) ifTrue:[

                tmp := self explainKnownSymbol:sym inClass:aClass.

                tmp notNil ifTrue:[ ^ tmp].

            ]

        ].

"/    ].

    "try for some obvious things"

    tmp := self explainPseudoVariable:string in:aClass.

    tmp notNil ifTrue:[ ^ tmp].

    "try syntax ..."

    tmp := self explainSyntax:string.

    tmp notNil ifTrue:[ ^ tmp].

    parser isNil ifTrue:[

        ^ 'parse error - no explanation'

    ].

    ^ 'cannot explain this (could not figure out what this is).'

    "Created: / 3.12.1995 / 12:47:37 / cg"

    "Modified: / 16.4.1997 / 12:46:11 / stefan"

    "Modified: / 23.3.1999 / 13:29:56 / cg"

!

explainHereIn:aClass

    ^ 'like self, here refers to the object which received the message.

However, when sending a message to here the search for methods

implementing this message will start in the defining class (' , aClass name , ')

instead of the receivers class (' , aClass name , ' or subclass).

Thus, using here, redefined methods will NOT be reached with a here-send.'

!

explainKnownSymbol:string inClass:aClass

    "return explanation or nil"

    |sym list count tmp commonSuperClass val s s2 

     firstImplementingClass cm msg|

    sym := string asSymbolIfInterned.

    sym isNil ifTrue:[^ nil].

    "try globals"

    (Smalltalk includesKey:sym) ifTrue:[

        tmp := '''' , string asText allBold , ''' is a global variable.'.

        val := Smalltalk at:sym.

        val isBehavior ifTrue:[

            val name = string ifTrue:[

                tmp := tmp , '

' , string , ' is ' , (val isLoaded ifTrue:['a'] ifFalse:['an autoloaded'])

, ' class categorized as ' , val category , '

in the ''' , val package , ''' package.'

            ] ifFalse:[

                tmp := tmp , '

' , string , ' is bound to the class ' , val name ,

' in category ' , val category , '.'

            ]

        ] ifFalse:[

            tmp := tmp , '

Its current value is ' , val classNameWithArticle , '.'

        ].

        ^ tmp.

    ].

    "

     try selectors

     look who implements it

    "

    list := Set new.

    Smalltalk allBehaviorsDo:[:c|

        (c implements:sym) ifTrue:[

            list add:(c name).

            firstImplementingClass isNil ifTrue:[

                firstImplementingClass := c

            ]

        ].

        (c class implements:sym) ifTrue:[

            list add:(c name , ' class').

            firstImplementingClass isNil ifTrue:[

                firstImplementingClass := c class

            ]

        ]

    ].

    (aClass canUnderstand:sym) ifTrue:[

        s2 := ('\\Instances of ''' , aClass name , ''' respond to #') withCRs , sym asText allBold

              , '\- inherited from ' withCRs, (aClass whichClassImplements:sym) name asText allBold.

        firstImplementingClass := (aClass whichClassImplements:sym)

    ] ifFalse:[

        s2 := ''.

    ].

    count := list size.

    (count ~~ 0) ifTrue:[

        "

         for up-to 4 implementing classes,

         list them

        "

        list := list asOrderedCollection sort.

        tmp := ' is a selector implemented in '.

        s := '#' , string asText allBold.

        (count == 1) ifTrue:[

            msg := s , tmp , (list at:1) , '.' , s2.

        ] ifFalse:[

            (count == 2) ifTrue:[

                msg := s , tmp , (list at:1) , ' and ' , (list at:2) , '.' , s2

            ] ifFalse:[

                (count == 3) ifTrue:[

                    msg := s , tmp , '

' , (list at:1) , ', ' , (list at:2) , ' and ' , (list at:3) , '.' , s2

                ] ifFalse:[

                    (count == 4) ifTrue:[

                        msg := s , tmp , '

' , (list at:1) , ', ' , (list at:2) , ', ' , (list at:3), ' and ' , (list at:4) , '.' , s2

                    ] ifFalse:[

                        "

                         if there are more, look for a common

                         superclass and show it ...

                        "

                        commonSuperClass := self commonSuperClassOf:list.

                        (commonSuperClass ~~ Object 

                        and:[commonSuperClass ~~ Behavior

                        and:[commonSuperClass ~~ Class

                        and:[commonSuperClass ~~ ClassDescription]]]) ifTrue:[

                            (list includes:commonSuperClass) ifTrue:[

                                msg := s . tmp , count printString , commonSuperClass name 

                                         , ' and redefined in ' , (count - 1) printString  

                                         , ' subclasses'

                                         , s2.

                                firstImplementingClass := commonSuperClass

                            ] ifFalse:[

                                msg := s , tmp, count printString , ' subclasses of ' , commonSuperClass name , s2

                            ]

                        ] ifFalse:[

                            (commonSuperClass == Object

                            and:[commonSuperClass implements:sym]) ifTrue:[

                                msg := s , tmp , count printString , ' classes.

All objects seem to respond to that message, 

since there is an implementation in Object.' , s2.

                                firstImplementingClass := Object

                            ] ifFalse:[

                                ((commonSuperClass == Behavior

                                 or:[commonSuperClass == Class

                                 or:[commonSuperClass == ClassDescription]])

                                and:[commonSuperClass implements:sym]) ifTrue:[

                                    msg := s , tmp , count printString , ' classes.

All classes seem to respond to that message, 

since there is an implementation in ' , commonSuperClass name , '.' , s2.

                                    firstImplementingClass := commonSuperClass

                                ] ifFalse:[

                                    "

                                     otherwise just give the number.

                                    "

                                    msg := s , tmp , count printString , ' classes.' , s2

                                ]

                            ]

                        ]

                    ]

                ]

            ].

        ].

        firstImplementingClass notNil ifTrue:[

            WindowGroup activeGroup withWaitCursorDo:[

                cm := firstImplementingClass compiledMethodAt:sym.

                cm notNil ifTrue:[

                    cm := cm methodComment.

                ]

            ].

            cm notNil ifTrue:[

                msg := msg , '\\The comment in ' withCRs , firstImplementingClass name asText allBold , ' is:\' withCRs , cm asText allItalic.

            ]

        ].

        ^ msg

    ].

    ^ nil

    "Modified: / 17.6.1996 / 17:09:30 / stefan"

    "Created: / 23.3.1999 / 13:29:33 / cg"

    "Modified: / 23.3.1999 / 13:40:40 / cg"

!

explainPseudoVariable:string in:aClass

    "return explanation for the pseudoVariables self, super etc."

    (string = 'self') ifTrue:[

	^ self explainSelfIn:aClass

    ].

    (string = 'super') ifTrue:[

	^ self explainSuperIn:aClass

    ].

    (string = 'here') ifTrue:[

	^ self explainHereIn:aClass

    ].

    (string = 'thisContext') ifTrue:[

	^ 'thisContext is a pseudo variable (i.e. it is built in).

ThisContext always refers to the context object for the currently executed method or

block (an instance of Context or BlockContext respectively). The calling chain and calling

receivers/selectors can be accessed via thisContext.'

    ].

    (string = 'true') ifTrue:[

	^ 'true is a pseudo variable (i.e. it is built in).

True represents logical truth. It is the one and only instance of class True.'

    ].

    (string = 'false') ifTrue:[

	^ 'false is a pseudo variable (i.e. it is built in).

False represents logical falseness. It is the one and only instance of class False.'

    ].

    (string = 'nil') ifTrue:[

	^ 'nil is a pseudo variable (i.e. it is built in).

Nil is used for unitialized variables (among other uses).

Nil is the one and only instance of class UndefinedObject.'

    ].

    ^ nil

!

explainSelfIn:aClass

    |sub|

    sub := aClass allSubclasses collect:[:c | c name].

    sub size == 0 ifTrue:[

	^ 'self refers to the object which received the message.

In this case, it will be an instance of ' , aClass name , '.'

    ].

    sub size <= 5 ifTrue:[

	^ 'self refers to the object which received the message.

In this case, it will be an instance of ' , aClass name , '

or one of its subclasses:

' , sub asStringCollection asString

    ].

    ^ 'self refers to the object which received the message.

In this case, it will be an instance of ' , aClass name , '

or one of its ' , sub size printString , ' subclasses.'

!

explainSuperIn:aClass

    ^ 'like self, super refers to the object which received the message.

However, when sending a message to super the search for methods

implementing this message will start in the superclass (' , aClass superclass name , ')

instead of the receivers class (' , aClass name , ' or subclass).

Thus, using super, a redefined method can call the original method in its superclass.'

!

explainSyntax:string

    "try syntax ...; return explanation or nil"

    ((string = ':=') or:[string = '_']) ifTrue:[

        ^ '<variable> := <expression>

'':='' and ''_'' (which is left-arrow in some fonts) mean assignment.

The variable is bound to (i.e. points to) the value of <expression>.'

    ].

    (string = '^') ifTrue:[

        ^ '^ <expression>